By comparison, IR conveyor dryers are smaller and often less expensive because they do not require insulation, and they can be shorter in length because IR radiation reaches ink-curing temperatures more rapidly and efficiently than heated air, particularly when curing plastisol inks. However, if items are conveyed through an IR dryer too slowly, the ink can overheat and break down chemically.

A relatively large IR dryer can cure approximately 1000 screen-printed items/hr and can cure thousands more per hour by adding one or more heating chambers, in addition to lengthening the conveyor and increasing its belt speed.

In terms of size, an infrared electric dryer that measures 7-8 ft in length (Figure 1) can cure approximately 300 items/hr, compared to 10-12 ft for a gas dryer of equivalent capacity.

Removing moisture
A common misconception is that forced hot air is needed to evaporate moisture from water-based inks and to expel it from the dryer. In reality, it is infrared radiation that heats the ink and causes evaporation, which is then removed from the heating chamber by a high-velocity exhaust system with high efficiency—on par with the efficiency of an IR dryer curing plastisol inks.

For example, an IR conveyor-dryer that exhausts 400 cu ft/min of air from the drying chamber and supplies roughly 500 cfm of air warms, but does not superheat, the air to pull moisture from the ink and exhaust it, and it prevents outside air from entering through the dryer exit.

Compare quartz to IR panels
If your application calls for an IR electric dryer, you can maximize results by understanding different ways in which infrared radiation is generated.

Some dryers use quartz tubes, while others use infrared panels. Because quartz tubes radiate 360°, they require a reflector to direct energy radiated from the top portion of the tube, back toward the garment. Infrared panels are made of a ceramic quartz fabric and are flat, directing virtually all energy toward the garment, offering higher efficiency (less power usage) per unit of radiation.

Quartz tubes are also relatively fragile and typically have a shorter life, whereas infrared panels often are more durable and have a useful life of up to 20 years, making them less costly in the long run.